Telephone amplification



March 19, 1940. H. KARL TELEPHONE AMPLIFICATION Filed Dec. 18. 19:56

5 Sheets- Sheet 3 H 1 wwvw wwwgwwwvwww wa u Patented Mar. 19, 19 40 UNITED STATES PATENT. oFmcE 11 Claims.

This invention relates to an amplifier that can be readily connected to and disconnected from any telephone at will. According to one modification of the invention this may be accomplished '5 by coupling the receiver or ear phone of any make of telephone to the amplifier or radio set, so that the person that has a conversation through the telephone does not need to hold the ear phone to .the ear and instead can use the one hand for writing down notes and the other hand for holding the pad or paper or other things. It is also to advantage to persons that have a temporary or telephone, whereby in such cases anybody can 20 easily step up or down a voice to such a degree that would suit the ear of the heater for better understanding the conversation.

. It is especially a need for public telephones where thousands of people of different capacities of hearing must use the same telephone. In this instance it must be mentioned also that fastidious people hate to touch or to hold to the ear a telephone receiver or ear phone which thousands of different people had used before. From a sanitary as well as from a practical view point the invention responds to' a public demand.

I am aware that amplifiers for telephones have been used already but these are of a different construction and the connections are of a different character and they are not constructed forthe use in pay stations whereby anyone can take advantage of them by inserting a certain coin.

One of the objects of this invention is therefore the creation of an amplifier or radio set 40 that is easily and quickly attachable to the receiver or ear phone of any telephone and therefore capable of amplifying the voice that is transmitted through the telephone connections.

Many men and women like to walk around while (Cl. 179-F2) A further object of the invention is the creation of diaphragms of mostly non-metallic consistency which are to transmit the voice of the speaker with greater clarity, resonance and volume than it is possible with diaphragms made from metal 5 alone which all create a shrill metallic sound that hurts the normal ear.

A still further object of the invention is to amplify the voice to such volume or strength that the bearer does not need to put the ear phone or 10 receiver to his ears. A still further object ofthe invention is to enable a person using a telephone pay station to amplify the voice of another person with which it has a telephone conversation by simply inserting a certain coin in the amplifyl5 ing outfit and that said coin causes various circuit connections which again connect the various circuits necessary for amplifying the voice over the telephone.

A still further object of the invention is to 20 enable a person using a telephone paystation to amplify the voice ofanother person with which it is connected over the telephone and to selec-' tively make such connections with push buttons or with a knob as will best suit the hearing with 25 out the need of employing the ear piece or receiver which, however, may be used by such persons that may not need the or want to'pay for amplification.

Still another object of the invention is the 30 particular arrangement of the. delicate parts of the amplifying apparatus that protects them from 1 destruction by mischievous persons.

Still another object of the invention is the use of the weight of a person to prepare the amplify- 5 ing apparatus in apay-station or booth for the use thereof and to, automatically restore all the mechanisms to a non functional state when that person leaves the floor of the station or booth.

Still another object of the invention is to auto- 0 matically record the amount of coins inserted in the amplifying apparatus at a pay'station.

Still another object of the invention is the creation of a receiver with such diaphragm that creates a clearer and more sonorous' sound than it 45 is possible with all-metal c liiphragms.

Still another object of the invention is the creation of a combination of a diaphragm of lacquered paper or cloth with an all metal diaphragm wherebythe paper or.cloth diaphragm 5 will create the correct sound waves while the all-metal diaphragm will transmit them for the transformation into electro-motive forces.

Still another object of the invention is the creation of means for momentarily shutting oil the voice coming over the amplifier and such means for damping a voice that is amplified in excess of the desired strength.

Still another object of the invention is the creation of a support with soft paddin'g'material that is adapted to exclude external sounds from the receiver or ear phone when coupled to the transmitter of the amplifier and said support having the impression of the shape of the receivers or ear phones front, and clasping means adapted to hold the receiver or ear phone close against the padding material near the diaphragm of the transmitter for the amplifier or radio set.

Still another object of the invention is the creation of novel arrangements in connection with the metallic diaphragm forobtaining the most desirable transformation of the sound into the electro-motive force for amplification.

Other advantages and features will appear in the detailed specification.

In the accompanying drawings which show the invention best suited for illustration the Figure 1 shows in elevation and partly in section the switch arrangement of the amplifying apparatus of a paying station in which the regular telephone transmitter and receiver is also installed and where for the simplification of service the customer may get amplification in three stages by the simple manipulation of pushing down one of a series of press buttons with one of which will be obtained an amplification to Normal voice" and with another to Loud" and with still another to Very loud", respectively; means for interrupting at will the voice heard over the amplifier and means for damping that voice are also employed.

Figure 2 shows an elevation partly in section on the line 2--2 of Figure 1 showing chiefly the mechanism for the preliminary functioning that is operated automatically when the coin is dropped in and which includes the setting of certain switches showing also the automatic recording of the amount of. coins that have been inserted.

Figure 3 shows an elevation partly in section on the line 3-3 of Figure 1 with parts broken away to show the switch arrangement from the side.

acteristics of a telephone line that is controlled at the central or connecting station; the transmitter and receiver on the left hand end of the telephone line being a pay station with telephone amplifier of the character exemplified in Figure 1 while at the right hand end of the telephone line is represented a transmitter and receiver that might be situated in a private home, or ofiice etc. where the amplifier is also connected to an antennae for receiving wireless transmission in form of a regular radio set whereby the telephone can be switched in and the radio connections with the antennae switched out.

Figure 5 shows schematically a typical three radio tube amplifying electrical diagram in which the various switching units are introduced that are shown in Figures 1 and 3; the receiver of the regular telephone is also shown being coupled in such way to the transmitter of the amplifying set that outside sounds will be kept out.

Figure 6 shows in section and somewhat enlarged the transmitter of Figure 5 and the parts of soft rubber for keeping out outside sounds.

Figure '7 is an enlarged sectional view of parts for holding the diaphragms of the amplifier transmitter as shown in Figures 5 and 6.

Figure 8 shows the scheme of keeping a special Figure 4 shows a circuit with the chief charamplifier transmitter and receiver apart from the regular telephone receiver (and transmitter) in order to prevent damage to the delicate diaphragms of the amplifier-transmitter.

Figure 9 shows. the details of the combined receiver and amplifier transmitter as used in the scheme of Figure 8, showing also a scheme for the transformation of the sound waves into electro-motive forces that is different from that shown with the transmitter of Figures 5, 6, and 7.

Figure 10 shows another scheme for protecting the delicate diaphragms of the amplifier transmitter from being damaged.

Figure 11 shows a receiver or ear phone with the improved diaphragm also used on the combined receiver transmitter of Figures 8 and 9 and of Figure 10.

Figure 12 shows in section and somewhat enlarged the diaphragm of the receiver of Figures 9, 10 and 11.

Figure 13 shows a front view of the diaphragm of Figure 12. I

Figure 14 shows in side view and partly in section a commutator with a dial that is also em ployed on the amplifier of the right hand end station of the telephone line shown in Figure 4 and which substitutes the push button switches of the amplifier of a pay station as shown in Figures 1, 2 and 3; the commutator is set at Normal voice strength.

Figure 15 shows the dial and knob of Figure 14 in front view.

Figures 16, 17, 18 and 19 show the positions which the movable contacts take on the commutator of Figure 14 while it is being turned the view is taken on the line ll|4 of Figure 14 looking to the left. In Figure 16 is shown the off position, in Figure 1'7 the position for the Normal" voice strength, in Figure 18 the position for Loud and in Figure 19 the position for Very loud;

Figure 20 shows schematically the way the commutator of the switching arrangement of Figures l4, 15, 16, 17, 18 and 19 can be automatically returned to the off position when the caller leaves the telephone booth.

Referring to Figures 1, 2 and 3 the numerals I, la, 2 and 2a designate the upright walls of a telephone booth of a so-called pay station that might be made sound-proof against outside sounds as known. 3 represents the floor of the booth which is spaced from the fioor 4 of the room in which the booth is situated. Floor 3 is pivoted as at 5 so that it will be moved on the pivots 6 when a person steps on it whereby the weight of that person presses the floor 3 down and keeps it in that position as long as it stands or otherwise keeps its weight on the floor. That person might even sit down on the seat I (seen in Figure 2) which can be moved up by turning it on a pivot 8 and secure it to the wall of the booth by suitable means, such as clamps, hooks, etc. so as to be out of the way when that persons prefers to stand. A standard 9 is pivotally so secured to the underside of the seat 1 that it will stand on the floor 3 when the seat 1 is brought into the horizontal position. The weight of that person sitting on that seat 1 is then also transmitted to the floor 3 and the latteris pressed down. Springs H) are chiefly arranged for returning the floor 3 to its normal uppermost position or level when the person leaves the booth which indicates that it has finished the conversation. Secured to the end H of the floor 3 are two vertical rods 12 and I3 which hold areas normal positions when the floor 3 is in its uppermost level in which said bar I4 is also pushed toits-up'permostposition. When the floor 3 and consequently also bar I4 is pushed down through the weight of a person the series ofswitch devices are then prepared for being used but they will not respond unless the various preliminarysteps are undertaken usual with telephone. First, the receiver I5 is to be taken from the hook |6 after thecorrect amount of coins has been introduced into the slot I1 and the" connection has -been made at the central station A shown in Figure 4 either by calling or, by other means new in use. a

-Whi1e the operator-at the central station A connects the caller with the phone demanded or before that or after it has become necessary to amplify a voice that could not be understood on account of being too feeble or distorted. the

caller has to droprthe coin, say a 5 cent'piece,

into the slot I8 shown'ln Figures 1 and 2 whereby the obstacle will be removed that otherwise would prevent the amplification of that voice.

Said obstacle consists partly of a pivoted lever] that is preferably of metal so as to have a certain weight. The pivot thereof that is indicated by 2| is secured to the booth wall 2a.

At its front end that lever 2|! has an extension 22 (see Figure- 2) with bevelled upper surface and that it forms a support that bears with its upper horizontal surface against the horizontal underside of the extension 22. Bolt 23 is retractable. against the tension of a spring 24 and that retraction is achieved through electro-rnagrietio Though mechanical non-electro-mag- I to restoreto or keep these switch bars in the position in which they interrupt the circuits to force.

netic means maybe employed, the use of an electro-magnet is preferable .because a greater pull can be exerted upon the bolt 23 than it would be possible with purely mechanical means on structures of that character'where a coin must a cause the action.

In order topermit the elctro-magnet 25 to attract the bolt,23 there is an iron bar 26 secured crosswise to the bolt 23 and distanced from the poles of the electro-magnet 25 only as much that it will be'attracted when the electromagnet becomes energized. "I'he winding 21 of that electro-ma'gnet- 25 forms part of a circuit that includes the battery 28,-two contacts 29 and 30 of which the latter is of a more springy. and

movable character than the contact 29. Contact 29 is connected to the battery 29 by means of the wire 3|. The winding 21 has one of its terminals connected to the wire 32' which leads to the other side of the battery '23 and its other terminal to wire 33 that leads to the contact 3|). Contact 36 is preferably made of a thin steel sheet that is. secured at some point in the slot l8 and which is distanced with its lower end a little from the contact 29 so as to normally keep the circuit open. Contact. 30 is therefore support on its front end and drops to the inclined position shown by the dotted lines. The coin 3|a thus rolls down on the then still more inclined upper surface channel provided for on that lever and drops into the box 32a through the slot 330. The box 32a may be secured to the wall 2a. A lock 34 keeps the front wall 35 locked that is so formed as to serve as a cover for the opening that permits the removal of the coins dropped. in the box. 35 is hinged to the box as at 36. The lever 20 will be restored to its normal horizontal position by the bar, 31 w'hich is secured with itsjone end- That cover or wall to the rod 3 (see Figure l) and with its other end to a rod 38 that is secured to the end H of' the floor 3. When the person leaves the booth, the floor 3,. rods I3, 38 and the bar 3! lift then the lever 20 and while moving into its horizontal ward again and forms the support for the,lever b The lever 20performs a number of functions, one of which is the setting of the switch-bar 22) passes said bolt whereby the latter snaps for- '40 to current conducting position when the lever 20 is in the inclined position and the placing of that switch-bar 49 into current interrupting position when the lever 2|! is in its horizontal position. For this purpose a bar 4| is secured to the lever 20 by one of its ends and passed through a hole at the lowermost part of the switch bar 40 and the other end of the bar 4| is suitably secured to a pivot 42. The electrical connections thus completed or interrupted will be described later. Another function whicl'i-lever 2|] performs in co-operation with the bar 4| is to allow the switch-bars 43 and 44 to be moved down when it (the lever 2|l) is in the inclined position and be described later when it (the lever 29) goes to and stays'in the horizontal position. While switch bar 40 will be pulled down by the bar ing each of the switch-bars 43 and 44 with a longer lower end partthat hasa relativelylong slot in which the bar 4| can move down without pulling these switch bars down. Bar 4| will move any of these switch bars 43 and 44 up again should they be moved down through means that will be described subsequently.

Another function which the lever 20 performs is that of moving a ratchet wheel 45 of a recording device one step farther every time it (the lever 20) 4 goes to its inclined position.

The spring sustained finger 46 that is pivoted to the lever 20 pushes the ratchet wheel 45 and when the lever 20 moves to its horizontal position the finger. 46 is moved into engagement with one of the next following teeth of that ratchet wheel by the spring 41. V

On the axle of the ratchet wheel 45 is secured 4|, the switch bars. 43-and 44 will stay in their I uppermost position. This is obtained by provida spool 48 to which is fastened the end of a ink every time'the pen touches the paper roll 59.

The collector of the dropped in coins may aflix the date of the collection, of the money right behind the last mark made'by the indicating device.

A still further function of the lever 20 is that of an electrical switch which when in connection with a circuit may cause the announcing at the central station or other place of the dropping of a coin in the slot of the amplifier.

In Figure 4 there is at 53 indicated in a diagrammatic way how the electrical connection in regard to the other circuit schemes may be made. In Figure 2 the stable contact is indicated by 54 and the movable contact by 55.

So far all those functions have been described that are performed by the apparatus when a person enters the booth and drops the required coin into the slot I8 which are the steps prior to the choosing of the degree of amplification of the voice heard over the telephone.

For better comprehending the electrical connections or disconnections which are performed by the switch bars that again are operated by the person using the buttons 56, 51 and 58, the diagram of the amplifying circuits of Figure 5 may serve. The button 55 that is shown in Figures 1 and 8 serves for adjusting the switch bar in such way as to cause the amplifier to increase the voice over the telephone to the strength of a normal speaking voice of a person standing in front of the listener. It is thus apparent that the first unit of the amplifier that includes the vacuum tube 6I must be so adjusted that an amplification up to the strength of the normal speaking voice will be obtained at the first output, which will be obtained through suitable connections with the secondary winding 62 of the transformer 63 and which include the wire I0, the contact 68, the current conducting part 66, the contact I2 and the wire II as far as the one of the terminals of the secondary winding 62 is concerned and the other terminal of that winding is connected by the wire 2I8' to which isconnected the wire 2I9 which again is connected to the loud speaker 64. It will be noted that also the secondary windings of the transformers I02 and I I2 are in electrical connection with the wire 2 I8 and through the wire 2 I9 with the loud speaker 64) While the amplifier is not used the switch bar 60 is therefore placed in such position that it will interrupt the electrical connection with the loud speaker 64 when the button 56 is in its uppermost position. In this position the switch bar 60 being rigidly united with the button 56 is also in its moved up posi tion. Ihis switch arm comprises two current conducting parts 65, 66 and an insulated part 61. A contact 68 that is pressed against the switch bar 60 by means of a spring 69 (see Figure 1) and which is connected by, the wire I0 to the second winding 52 of the transformer 63 contacts with the insulation 61. To the conducting part 66 may be affixed the wire II that leads to the loud speaker 64 but according to the drawings there is a special contact 12 so arranged opposite the contact 68 that it presses against the switch bar 60 through the urge of a spring I3 so that the contact 68 will have an adequate counterpressure at all times. Another pair of contacts I4, I5 is arranged similarly to the contacts 88, I2 but they contact with the conducting part when the switch bar 60 is in its uppermost position. In this position an electrical connection is created between the second winding 62, the wire I0, respectively, and the grid I6 of the second vacuum tube 'I'I whereby the wire I8 electrically connects the contact I5 with the grid I6.

If all the connections are intact that create the electro-motive force set up in the transformer 63 which includes also the then pushed down switch bar 40 with its conducting parts 19, that are then contactedby the contacts 8|, 82 and 83, 84, respectively, whereby the circuits for the filament 85 and for the plate 86 will be closed thereby, that electro-motive force will be transformer into sound waves by the loud speaker or cone 64 when the button 56 and consequently the switch bar 60 is pushed down whereby the contacts 08, I2 come into electrical contact with the conducting part 66. The contacts I4 and I5, however will come into contact with the insulation 61 whereby the electrical connection between the second winding 92 of the transformer 63 will be cut out from the grid I6 of the vacuum tube 11.

Assuming, however, that the amplification through the connections so far described are not sufiicient for the listener on the amplifier and that a still greater amplification is. desired which would be denominated Loud according to normal standards of hearing, the second button 51 is to be pressed down which thereby will bring the spring urged contacts 88, 89 into contact with the conducting part 90 of the switch-bar 9|. The spring-urged contacts 92 and 93 would then come in contact with the insulation 94 and the switch bar 43 which thereby will be pushed also to its lowermost position through the switch bar 9I will bring the conducting parts 95 and 96 into contact with the spring urged contacts 91, 98 and 99, I00, respectively. The result is then the electrical connection between the second winding IOI of the transformer I02 with the loud speaker 64 by means of the wire I03, contact 88, conducting part 90 of the switch bar 9|, contact 89, wire I04 and wire I05.

Furthermore, the interruption of the connection is also obtained between the wire I03 and the grid I06 which latter is electrically connected with the contact 93 by the wire I01 while the contact 92 is connected by the wire I08 to the wire I03; furthermore, the closing of the circuit for the filament I09 through the contacts 91, 98 and the conducting part 95 is also obtained as well as the closing of the circuit for the plate IIO through the contacts 99,,I00 and the conducting part 96.

For a still greater amplification denominated Very loud another vacuum tube II is used together with the circuitsnecessary therewith including the transformer II2 whose second winding H3 is connected tothe wire III. The switch bar II 5 to which is secured the push button 58 is similar to the switch bar 60 and the switch bar 9I and serves for the electrical connection of the wire I I4 with the wire I05 by means of the spring urged contacts H6, H1 and the conducting part II8 when that switch bar is pushed down. Other contacts pressed against the switch bar II5 would have a useful purpose only when further amplification would be made through a fourth or more vacuum tube or tubes.

The switch bar 44 which will be pressed down by the switch bar II 5 when the latter will be pushed down, closes the circuits of the filament H9 and of the plate I20 throu h the spring urged'contacts I2I, I22, the conducting part I23, the spring urged contacts I24, I25 and the conducting part I26, respectively.

In order to have an amplification either Normalvoice, Loud" or TVery loud it is necessary to have the two other upper switch bars pushed up that are usedfor the other stages of amplificationso that the electro-motive force will be concentrated only to the one stage of the amplification desired. If, for instance, the switch bar 60 is pushed down, the switch bars 9| and H must be pushed up so that the loud speaker 64 will be influenced only by the electro motive force set up in the coil 62,

If, however Loud is desired and consequently the switch bar 9| is pushed down, the switch-bar 60 and the switch bar H5-must be pushed up, first in order to avoid a louder voice than desired and furthermore to have the connections over the contacts 14, and the conducting part '65 in alignment so that the grid IE will receive the impulse from the electro-motive force set up in coil 62'. F

Should then Very loud be desired as the degree of amplification and consequently the switch of such construction that they snap into the position in which they are forced by the pressure of the respective switch bar that is pushed down. There are three of them and more would be needed if a stillgreater amplification and consequently more switch bars would be employed. I Y

The first one of the double shank levers has its two shanks indicated by I30 and HI and it is shown that they are diverging irom'their common pivot I32 at different angles that are so chosen that one shank as, for instance that indicated by I30 will push up its respective switch bar or-simply moves up should that switchbar be pushed up already when the other shahk which in this instance would be that indicated by I3I is pushed down by the switch bar 3|. If

then the switch bar pushes down the shank I30, the shank I3Iwil1 then push. up the switch 1 bar 9|. The pivot I32 is journalled in a hearing I33 that has an aperture that is downwardly elongated so that the pivot may move downward against the tension of a spring I34 that is so secured to the part forming the bearing thatit bears with its two ends against both shanks in such way that only a relatively strong pressure exerted upon the shanks and the pivot mywill move thelatter to' the lower part of that bearing. Above that pivot .I32 of which another one may be employed at the opposite rear side .there is a little elevation'or extension I35.

which touches the horizontally directed upper wall of the part forming the bearing 533 which is firmly secured to the board I36. The extension I35 is then always urged by the spring I34 to snap into the corner to which'it is nearest-and this gives the snapping down, and-up function to the buttons which is necessary for creating complete electrical connections, disconnections, re-

spectively. The other two shanked levers I31 and I33 are of a similar construction and it deems unnecessary-to describe the structure of them with the exception that. the one indicated by :21 has one shank tie-smacwith the switch bar 9| and the other with the switch'bar H5 while the'double shank lever I38 having relatively longer shanks than the previously men- Y tioned has one of'its shanks arranged as to .be

engageable with the switch bar 60 and the other with the switch bar H5.

it will be remembered that the switch bar 40 must be in pushed down position no matter the switch bar 60 is pushed down or not should any of the other switch bars Si or H5 be used.

This switch bar 40 is therefore operated auto- .mat ically and independently from the other switch bars. The switch bar 43, however, will be pushed down by the switch bar ill. The switch bar 44 will be pushed down by the switch bar H5 and at the same time will push down the switch bar 4.3 by means of a bar I2'I, that is secured by its one end to the lowermost part of the switch bar 44 and which engages the upper side of an'extensiou I28 that is provided for at the lower end of the switch bar 43. ,If the switch bar 43 is pushed down by the switch bar 9| the switch bar 44 will therefore remain in pushed up position unless it is pushed down by the switch bar H5.

For creating suflicient surface upon which the various parts such as the double shank levers, the lower switch bars and the bar I4 have to bear. upon, each of the three switch bars 60, SI and H5 has a horizontally directed extensioni secured to the lowermost end thereof as best seen in Figure 3 where the extension belonging to the switch bar H5 is indicatedby I23. These extensions reach into the recess formed by the under side of' the upper switch board I36 and the lower; switch board I8. 1 Itis apparent that any other suitable switc arrangement could substitute the switch bars. There might be used knife switches or others and in this respect the commutator scheme in connection with a dial as illustrated by the Figures 14, 15, 16, 1'7, 18 and 19 will suit the purpose. This scheme can be employed in connection with I any radio set that has amplification in the degree as, desired. It is therefore suitable for privately owned radios such as is supposed to be the one on the extreme right of Figure 4 which shows an-antennae I40. By the use of the switch dial I4I the/antennae can beswitched out o! communicationwith the remainder of the radio set and the latter may be switched thereby to the telephone transmitter of that set that will be described subsequently.

Referring more particularly to Figures 14, 15, 16, 1'7, 18 and 19, 'a dial I42 of the usual construction has the inscriptions Normal voice Loud, Very loud and Off and these indications are' so placed that each occupies'one quarter of the circular space left for them. That certain space correspondsagain with the positions of the contact strips I43, M4 I45 arranged on the commutator I46 in respect to a series of spring urged contacts'.

In the o po'sition'as shown in Figure 16 'the contact strip m which is shown in full lines in the Figures 16, 17, 18 and 19 is shown as contacting with the contacts In only. Since, however. an electrical connection with the loud speaker 64 and the secondary coil 62 of the transformer 63 (see also Figure 5) will be established by said contac't strip 3 'onlythrough the connection between the contacts I41 and I48'the commutator must be 'tih'ned a quarter turn whereby the contact strips take the position as shown in Figure 17.

If Loud is desired another quarter turn must be made of the commutator by means of the knob I50. The contact strip I44 indicated by dotted lines in Figure 18 will then come into contact with the contacts I5I and I52 which creates an electrical connection with the loud speaker 64 and with the second winding IOI of the transformer I02 (see Figure 5). The contact strip I43, however, will then be out of contact with the contact I41 whereby the connection of the secondary winding 62 with the loud-speaker 64 will be interrupted. In this position, however, of the contact strip I44, connection of the wire 10 with the grid 16 of the vacuum tube 11 must be established (see Figure 5') and this can'be done by a special contact strip also arranged on the commutator and indicated by I53 which then contacts with the two spring urged contacts I54,

To have the voice amplified to Very loud another quarter turn of the commutator will bring the contact strip I into contact with the contacts I56, I51 as shown in Figure 19. In this instance the connection between the wire I03 of the secondary winding IOI of the transformer position. The contact strips are indicated by I6I,

I62, I63 and they are discontinued at the sector that represents the off position. Each con- 'tact strip is contacted by two contacts I64, I65,

I66, I61 and I68, I69, respectively, each pair being placed side by side but a little distanced from each other. The contact I64 will then substitute the contact 8| while its next neighbor contact I65 will substitute the contact 82 of Figure 5 and the contact strip I6I will substitute the contact part 80. In a similar way will the contact strip I62 substitute the contact part 95 and the contacts I66, I61, the contacts 91 and 98. respectively, while the contact strip I63 will substitute the contact part I23. and the contacts I68, I69 will substitute the contacts I2I, I22, respectively.

Since it appears that suflicient interruption of the circuits is obtained therewith while the telephone amplifier is not in use no other arrangements of contacts for this purpose will be necessary.

the upper part of rod I3 and the bar I4. In this instance the lever 20 while being in its lowermost position has to make an electrical connection through some contacts shown by dotted lines and indicated by I10 and HI that have to connect the wire I12 with the battery I13 (shown in Fig ure 5) which will make the amplifier ready for its purpose. As it is desirable to have some means for automatically turning the commutator I46 to the off" position when the caller leaves the telephone booth there is a relatively simple mechanism employed that is illustrated schematically in Figure 20 and which consists of a flexible member I15 that is secured to some suitable part of the insulation of the commutator I46 but exactly at the opposite side of the middle of the 011 section thereof which corresponds also with the inscription off" on the dial. At the other end of that flexible member I15 is secured the weight I16 which should be just heavy enough while falling or descending to unwind the flexible member I15 and to thereby turn the commutator I46 to the position in which off will be situated at the uppermost part of the commutator, should that commutator have been turned by hand into another position. In order to avoid the dropping of the weight I16 and the returning of the commutator to the "off" position as soon as the caller removes the fingers from the knob I50 (see Figure 14) there. is another flexible member I'I1 (see Figure 20) secured to the weight I16 and passed over two pulleys I18, I19 and by its other end it is aillxed to the farthermost point of an extension bar I that is afiixed to the lever 20. The weight of the lever 20 combined with that of the extension I60 must be in excess of that of the weight I16. It is thus evident that when the lever 20 drops together with its extention I80 the weight I16 will be pulled up to its uppermost position, thus allowing the caller to turn the commutator I46 to any of the positions he desires for the amplification of the voice over the telephone without the commutator being immediately returned to the off position. As soon, however, as the lever 20 together with its extension I60 is moved up by the bar 31 (see also Figure 2) to the horizontal position the weight I16 descends and pulls the flexible member I15 thereby returning the cornmutator I46 to the off" position.

An essential part of the invention is the creation of means that permit the instantaneous connection of the amplifier or any radio set with the telephone. In this connection there are two types that may be employed, namely one that is permanently so installed that simply an automatic (through the introduction of a coin etc.) or manually operated switch will perform the connecting with the telephone and disconnection with the antennae if it deals with a private owned radio set and the other type where the receiver of a telephone outfit is simply coupled to a transmitter of the amplifying apparatus. The last mentioned type for connecting the telephone and which is also employable both in pay stations and with private owned radio sets consists of the transmitter I82 (see Figures 1, 4, 5, 6, 1, and 10) which is provided with a support I83, consisting of a layer of padding material, preferably of soft rubber or sponge rubber for the purpose of preventing outside sounds from mingling with those perceived at the receiver. I5 which latter is simply laid on that support made of padding material whereby a spring I presses the receiver I5 against the portion I81 of said padding material that surrounds and partly covers also the front opening of the transmitter I82. The part of the support I83 with the padding material I61 against which will be laid the receiver, must have the recessed impression of at least part of the receiver that will enable the receiver to lie snugly against that padding material. There might be one or more clasps I86 employed for For most of the pay station's it will be necessary to'keep'the transmitter fofthe amplifier as well as a special telephone receiver that is coupled thereto, out of reach of the customer in order that no damage .is done tothe delicate diaphragms thereof.

It will therefore be necessaryto have a special telephone receiver arranged that is permanently coupled to the transmitter of the amplifier. Such scheme is illustrated in Figure 8 and in Figure 9 is shown the enlarged detail.

This amplifying outfit is 'of the pushbutton character already described in connection with Figures 1, 2 and 3, but it might just as well be of the character ofthe type shown with the Figures 14 to 20 inclusive and this refers also to the other couplings 'of the receivers with the transmittersof the amplifier shown in the drawings.

In Figure 8 there is the usual outfit of a tele- Y phone shown similar to Figure 1 with the tele- ,phone box 81 having a coin drop I1, the trans-- 'mitter 208, and the receiver I5. To one of the wires I84 of the receiver I there is, however, anr 1 the separate receiver I90,'while' the wire I88 secured tothe contact I92 of a switching device employed for the with push button I93 that serves for temporarily interrupting the voice coming over the telephone. There is a current conducting contact part I94 normally contacting the two contacts I82 and I95 and a spring I96 is arranged for always returning the contact I94 to the position in which it contacts ,with the contacts I92, I95 in which position the push button I 93 is pushed up. There is a wire I01 connected to the contact I95 and then connected at I99 to'the winding200 of the receiver transmitter I90 (see also Figure 9) In Figure 1 there is also the push button I93 purpose of interrupting the voice coming over, the loud speaker 64. There is, however, a little modification in the arrangement because it is to interrupt the-electric connection between the wire 244 and the grid 245 (see Figure 5) and since there is only one receiver avail- ,able this receiver had to be unclasped'and taken from its support I83 if only the weak voice of that receiver is preferable for any reason whatsoever. The scheme in 'connectionwiththe push button I93 shown in Figure 1 could, however,'be employed also in connection with the amplifier of Figure 8 inwhich case the wire I88 would be directly connected to the winding 200.-

The windings m, 200 of Figure 9 being the same circuit have the cores f, 202 slightly protruding at the side where-they face the daphragm 203a. At their other ends'theyare gecured to the permanent magnet 204 as usual.

The diaphragm 203 (see also Figures 12 and 13) might be .of the usual construction and might be of metal but in order to avoidthe socalled metallic shrillness common with the voices transmitted through the all metal, diaphragms and for obtaining greater resonance,

clarity of the words spoken and the elimination.

of by-sounds there is paper 01' the typewriting type used. That paper may have the rough texture common with such paper. Instead .of'

paper, however, there might be silk employed although paper is preferable. The paper or silk is then stretched on the frame 205. If it deals with paper, the sheet must be made wet with water when being mounted on the franie 205 so that it will be well stretched when it has dried.

' When completely dry it receivesa coat of lacquer "of a quality that dries hard. It might be the 'tions which will face the cores 20I, 202.

' lacquer and are held fast by the latter and since thereof slightly touch the respective right side it will be these iron particles that are attracted by the electro-magnetic flux of'the cores 20I, 202 the iron particles being held ,fast byfithe lacquer move also the lacquered paper in the vibrations transmitted by the electro-magnetic impulse. whereby the sound waves are produced-by the vibration. of the lacquered paper "diaphragm." The cores 2 0I, 202 should be distanced from the diaphragm 203 by about one thousandth of an inch. l

This scheme is employed also with the transinitters illustrated in Figures 5,6, 7, 10 and could be used with 'the transmitters of Figures 1 and 4. In Figure 11 in which a receiver is shown, the same scheme is.also employed. There is an advantage over'other kinds of transmitters because it can be tested upon clearness of sound and other qualities before it is assembled with.

the other parts of the transmitter.

These parts are dependent upon the vibrations of the diaphragm. 203. It is therefore preferable to create direct contacts such as indicated by 206 which may consist of a thin piece of cork or of the light marrow of some plant. This piece is secured to the center part of the diaphragm 203 and might be secured also to the next part which is the metallic diaphragm 201. vIt is how'- ever, preferable to have the part 206 notsecured thereon whereby also the paper or silk diaphragm which will have the reference numeral 203a will be completely stretched. It isto men-.

tion that whenever silk is used for the diaphragm 203a that 'silk must receive one or several coats 'of hard drying lacquer.

The diaphragm 201 might metal such as steel, copper, a1 it is connected in an electrical circuit it should be insulated from the part 205 as well as from the diaphragm 203a. It is also to mention that the air or some gasin .the space between the diaphragm 203a and the diaphragm 201' will transmit the sound'v'ibrations of the diaphragm 203a to the diaphragm 201. For transforming the vibrations of the diaphragms 203a and 201 into electrical vibrating impulses various methbe of any suitable umand since I ods can be employed. While there is in Figures 5 and 6 a relatively large number offine copper or silver filaments 208 secured to a copper plate 2! and which are so bent that the other ends of the diaphragm 201 there are carbon granules employed in the scheme shown in Figure 9. In

'Figures 5 and 6 it is shown that to the copper plate -2I0 is directly connected the primary winding 2 of the transformer 2I2 The secondary winding is indicated by 2I3.-

The electrical" circuit connections-with these windings are shown in Figure 5 and. will be traced later. The carbon granules 2I1 employed in the scheme of Figure 9 are placed into a number'of partitions or chambers 2l5 which each are separated from the next partition or chamber by an extension 2? of mica that is secured to'the copper plate 2l0 and which does not completely reach the diaphragm 201. The carbon granules are thereby prevented from being concentrated upon one heap because they would fall to the bottom of the large space if the extensions 2IE were left away'. In the scheme shown in Figure 9 they are evenly distributed over the surface of the diaphragm 201 and are not packed but each chamber 215 is provided with its certain amount of carbon granules that make vibrating contacts between the diaphragm 201 and the copper plate 210.

Instead of the filaments 209 and of the carbon granules there might be a .gas introduced that has electricity conducting properties as, for instance mercury fumes or vapors or others known to science and should be confined in the space between the diaphragm 201 and the copper plate 2).

Referring to Figure 11 which represents a receiver that might be constructed with a regular handle or only as an ear-phone, the part that distinguishes this receiver from these up to date in use is the diaphragm 203 made of paper and provided with the lacquer coating and the iron files or still smaller particles of iron in the lacquer as illustrated in Figures 12 and 13 and described already in connection with the diaphragm 203a of Figures 5, 6, '1 and 9, whereby, however, the parts are left away that belong already to the transmitter such as the connection 206 and the diaphragm 201 etc. If this receiver is simply used as an ear phone it can be coupled to the transmitter of Figures 5, 6, '7, 10 by means of the clasp 220 which is constructed in the fashion to snap against the hull of the receiver to press the latter sufficiently strong against the padding material I81 of the amplifier receiver. It distinguishes itself also from the clasps I86 in that no additional closing piece is necessary.

The snapping-on action is obtained through the pointed or edge forming extension 22! that is in touch with a part 222 that has two sides 223, 224 converging to an edge 225 whereby a relatively strong spring 226 of suitable forum-- tion presses that piece 222 against the extension 22l. In the drawing of Figure 11 it is shown that the clasp 228, that is movable on the pivot 221, is pressed by the'part 222 against the underside of the extension 22l, thus moving and pressing the part 220 firmly against the receiver hull. If the part 220 will be lifted which requires the amount of strength that will overcome that certain part of the tension of the spring 226 the side 224 of the part 222 will then press against the upper side of the extension 22I whereby the clasp arm 220 will snap into the raised or open position.

Being pushed down the part 22l snaps against the underside of the extension 22I forcing the clasp arm 220 against the hull 228 of the receiver.

Referring to Figure '10 there is a structure shown with which the reaching with the finger or with some tool of the easily -destroyable diaphragm 2830. of the amplifier transmitter, is prevented. For this purpose a relatively large space,

which is'the resonance-chamber 231i, is created and having the wall 23| so inclined that the sound coming from the diaphragm 203 or from by the dotted lines 236.

any other'diaphragm of the receiver 15 will be reflected towards the diaphragm 203a as shown The wall 23! is preferably made of wood and concave in shape as shown, for obtaining an agreeable modulated sound. It is shown that the aperture 235 to the resonance chamber 230 which will be open when the receiver I5 is removed and hooked up in the fashion as shown in Figure 8 the diaphragm 203a will not be reached with the fingers or with some tool on account of the extension 231 reaching in a protecting way far into the resonance chamher 230.

The diaphragm 201 is best secured in the way as shown in the enlarged detail view of Figure '7 in which the border part of that diaphragm is grasped by a copper or brass frame 239. The wire 24!! (see also Figures 5 and 6) is inserted into a hole in theframe 239 and pushed in as far as to touch the diaphragm whereby not only a good contact with the frame 239 is created but also a direct contact with the diaphragm. As shown in Figure 5 the wire 240 is conducted to one side of the battery I13 and to the other side of that battery is connected the wire 242 that is also connected to the contact 111 previously mentioned. The secondary winding 2l3 has one of its terminals connected to the wire 244 which leads to a contact 244a that contacts with the movable contact 243 and the latter with a contact 249a and the wire 249 that is connected to that contact leads to the grid 245 in the vacuum tube 6|. The other terminal of the secondary winding 2l3 is connected by the wire 246 which leads to the contact 83. The connection with the primary winding 241 of the transformer 63 is therefore interrupted through the insulation situated between the contacts 83 and 84 when the switch bar 40 is pushed up. In its pushed down position it will bring the current conducting part 19 into contact with the.contacts 83 and 84 and the wire 248 leads to and completes the connection with the primary winding 241.

Similar arrangements are made in connection with the other units of the amplifying outfit whose description of the various circuits is deemed unnecessary. This refers as well to the circuit arrangement shown in Figure 4 and it is mentioned only that A is the central or connecting station, B a pay telephone sub-station equipped witha transmitter T2 and receiver R2 and with an amplifier and C is a telephone with a transmitter T3 and a receiver R3 that can be coupled to an amplifier that is convertible into a radio and supposed to be situated in a private home but for convenience it is called a station. In the diagram of Figure 4 it is shown that the switch 250 has been connected to the line wire after the bulb 25l over the grounded circuit did light up upon a call from station B through the connection at 53 with the contacts 54, 55 or otherwise through the hook [6. The operator in the central station did not connect the station C yet but by closing the switch 252 and pressing down the spring returned ringing button 253 the buzzer 254 will be sounded in the station C through a grounded circuit that includes one of the line wires indicated by 255. By connecting the plug 256 with the line wire 251 the connection between the station E and C will be established because the other line wire 258 terminating in station C is permanently connected to the line wire 259 that terminates in station B and other stations. .There is also a transmitter TI and a receiver RI in the central s areas. station A as usual. It will be noted that the talker will hear his own voice over the telephone whichis of advantage because he or she can thereby find out how loud to speak or how far to subdue the own voice. Means in form of the push button switch I93 describedin connection with the Figure 8- enables the speaker at the telephone tocut out his own voice over the amplifler, should itprove disturbing; by simply pressing with the finger on P-the' push button I93 while atthe withdrawal of the finger from the button the voice from the other connected station as-well as the own voice will be heard through the amplifier. If only the very low voice of the receiver I will be sufficient temporarily then the receiver I5 should be used and according to Figure 8 the push button I93 pressed down simultaneously. The switches 260, 26I may be automatic and opened for avoiding short circuit when the bell 262 or the buzzer 254' shall be sounded. v

In case that the listener at the amplifier would like to have the strength of the voicesomewhat reduced, as, for instance to half the strength between Normal? and "Lo ud or between Loud and "Very loud there is a covering means 269 arranged as shown in Figure 1 that has to act as a damper and which may be, moved to cover the whole front side of the loud speaker 64 .or only a part of it. This covering means or damper 263 ,is preferably hinged to the frame of the loud speaker 64 in order that it can be moved over the. front side .of the latter and also moved out of that front side-as shown in the drawings; An inscription on the front side of that damper might behad to inform the listener of the purpose and use of the damper. That inscription might have the'wordingt- If voice over the amplifier is too loud use this damper and move it completely or partly over the loud speak- On the front side panel 266 preferably behind the buttons 56, 51, 58 and I93 or on the front side panel 261 of Figure 14 directions for the useof the amplifier maybe had so that also, ,people without the experience of using the amplifier may readily understand how to operate it. Beside these inscriptions the various buttons 56, 51, 56 should show the words Normal voice, "Loud, Very loud, respectively and referring to the button I93 the inscription should read :For interrupting the voice over the loud speaker. for hearing that direction a special plate 268 may be provided for and placed directly behind the button I93 so that the user of the amplifier may be able to read it.

The representation in the drawings of the stepping up scheme of the voice is only illustrative and .0 there might be. more electrical energy put up for obtaining the various amplifications. It must be remembered also that there are other parts that, contribute to the amplification, as, for instance the receivers and transmitters of special Q construction as set forth to which also the loud speaker is to be counted and which distinguishes itself from the other receivers only through the much larger size of all its parts.

Having described my invention what is claimed is:

1. In a telephone amplification system, a telephone station comprising a receiver and a transmitter, a second receiver at said station, a trans emitting device permanently coupled to said second receiver, an amplifying set connected tosaid Since the button I93 may be too small transmitting device, and comprising a loud speaker, and switching means incorporated in said telephone station for controlling electric circuits of said amplifying set for selectively varying the volume of sound reproduced in said second receiver and transmitted through said amplifying set. 5

2. In a telephone amplification system, a telephone station including a receiver, a transmitter, means to couple said receiver to said transmitter, an amplifying device connected to said transmitter, means atsaid station for selectively increasing; the volume of sound into said receiver and through? said amplifying device, coin-controlled means for rendering efi'ective said selective means, and means also at said station for auto matically interrupting: the operation of said amplifying device when a person leaves said station.

3. In a telephone amplification system,'a volume control apparatus consisting-of a plurality of electrical switches including selectively operable push buttons for actuating the 'same, an

amplifying device including electrical circuits and vacuum tubes for the amplification of sound, said device controlled by said switches for energizing the same when said switches are selectively operated, and means to automatically restore said switches and push buttons after the same have been operated. f

4. In a telephone amplification system, a volume control apparatus consisting of a plurality of electrical switches including selectively op erable push buttons for actuating the same, an

operable electrical switches arranged on'said commutator and including contact strips and associated pairs of contacts, an amplifying device controlled by said switches and including electrical circuits and vacuum tubes for obtaining different degrees of sound amplification in accordance with the selective operation of said switches, means'to operate said commutator to selectively energize said circuits to produce such modulation, and means to automatically restore said commutator to a non-functioning position to interrupt said electrical circuits through said contact strips and contacts. a I

6. In a telephone amplification system, a volume' control apparatus comprising I electrical switches including contacts, means to manually and selectively operate said switches, an amplifying device includingelectrical circuits and vacu um tubes for the amplification of sound to various degrees, said circuits being electrically connected to said contacts and selectively energized by the operation of one or the other of said switches to alter said amplification through said tubes, and means to' automatically restor said switches to inoperative and circuit interrup ing positions.

7.-In a telephone amplification system, an apparatus including a receiver having a vibratory member consisting of a magnetizable sheet, an

electromagnet having cores disposed in proximity to said vibratory member to vibrate the same in accordance with the degree of energization of said electromaguet, a transmitter including a metallicmembrane coupled to but electrically insulated from said receiver, a vibration transmitting connection between said vibratory member and said membrane, transmitting means operatively contacting said membrane for transmitting electromotive forces in harmony with the vibrations of said receiver and transmitter,

a transformer having primary and secondary windings, and a circuit including said primary winding of said transformer and said metallic membrane to transmit the electromotive impulses created by the vibrations of said membrane to the secondary winding of said transformer.

forces created in said circuit and accentuated bysaid vibrations, and a transformer having primary and secondary windings, said electric circuitfurther including said metallicmember and said primary winding for transmitting electromotive impulses to said secondary winding in conformity with said vibrations.

9. In a telephone amplification-system, a transmitter having a vibratory membrane, a plate slightly spaced from said membrane, filaments secured to said plate in contact with said membrane, a transformer having primary and secondary windings, and an electric circuit including said membrane, filaments, plate and primary winding energized to transmit impulses to said secondary winding'in'coniormity with the vibrations or said membrane." 5

10. In ,a telephone amplification system, a sound volume control apparatus, comprising selectively operable electrical switches arranged for obtaining immediately one of three diflerent stages of amplification, namely, an amplification selectively close those of said circuits to produce.

such selected amplification, and means to automatically restore those switches to a non-functioning position that areoperatively connected with those circuits and tubes that amplify said sound above the selected degree, and means for automatically nullifying any amplification over said sound volume control apparatus. 11. In'a telephone amplification system, an

apparatus including a receiver having a vibratory member consisting of a fibrous ,sheet with" iron filings embedded in it, rendering it magnetizable, an I electromagnet having cores disposed in proximity to said vibratory member to vibrate the same in accordance with the degree oi energization of said electromagnet, a transmitter including a metallic membrane coupled tobut electrically insulated from said receiver, a vibration transmitting connection between said vibratory member and said membrane, transmitting means operatively contacting said membrane for transmitting electromotive forces in harmony with the vibrations of said receiver and transmitter, a transformer having primary and secondary windings, and a'circuit including said primary winding of said transformer and also said metallic membrane to transmit the electromotive impulses created by the vibrations of said membrane to the secondary winding of said transformer.

HEINRICH KARL. 

